KR20110008105A - Fluid droplet ejecting - Google Patents

Abstract

Fluid droplet discharge systems are described. The system includes a substrate having a fluid body including a fluid pumping chamber, a descender fluidly connected to the fluid pumping chamber, and a nozzle fluidly connected to the descender. The nozzle is arranged to discharge fluidic droplets through an outlet formed in the outer substrate surface. The flow passage body also includes a recirculation passage fluidly connected to the descender. The fluid droplet discharge system also includes a fluid supply tank fluidly connected to the fluid pumping chamber, a fluid return tank fluidly connected to the recirculation passage, and a pump fluidly connecting the fluid return tank and the fluid supply tank. In some embodiments, the flow of fluid through the fluid body is at a flow rate sufficient to draw bubbles or contaminants through the fluid body.

Description

FLUID DROPLET EJECTING

The present invention relates to a fluid discharge device.

In some fluid discharge devices, fluid droplets are discharged onto the medium from one or more nozzles. The nozzle is fluidly connected to the flow path containing the fluid pumping chamber. The fluid pumping chamber may be operated by an actuator that results in the discharge of fluidic droplets. The medium may be moved relative to the fluid discharge device. The discharge of fluid droplets from a particular nozzle is timing with the movement of the medium to position the fluid droplets in the desired position on the medium. In these fluid ejection devices, it is usually possible to eject fluid droplets of uniform size and velocity in the same direction to provide uniform deposition of fluid droplets on the medium.

In one embodiment, the systems, devices, and methods described herein include a system for ejecting fluidic droplets comprising a substrate. The substrate may include a flow path body in which a flow path is formed. The flow path may include a fluid pumping chamber, a descender fluidly connected to the fluid pumping chamber, and a nozzle fluidly connected to the descender. The nozzle may be arranged to discharge fluidic droplets through an outlet formed in the outer nozzle layer surface. The recirculation passage may be fluidly connected to the descender and may be closer to the nozzle than the pumping chamber. The fluid supply tank may be fluidly connected to the fluid pumping chamber. The fluid return tank may be fluidly connected to the recycle passage. The pump may be configured to fluidly connect the fluid return tank and the fluid supply tank.

In another embodiment, the fluid droplet dispensing apparatus may include a substrate on which a fluid pumping chamber is formed. The descender may be formed in the substrate and fluidly connected to the fluid pumping chamber. The actuator may be in pressure communication with the fluid pumping chamber. The nozzle may be formed in the substrate and fluidly connected to the descender. The nozzle may have an outlet for discharging fluid droplets, which may be formed on the outer substrate surface. The recirculation passage may be formed in the substrate and fluidly connected to the descender at a distance between the outer substrate surface and the nearest surface of the recirculation passage less than about 10 times the outlet width, and the recirculation passage may be fluidly connected to different fluid pumping chambers. none.

In another embodiment, the fluid droplet dispensing apparatus may include a substrate having a fluid pumping chamber formed therein, a descender formed in the substrate and fluidly connected to the fluid pumping chamber, and an actuator in pressure communication with the fluid pumping chamber. The nozzle may be formed in the substrate and fluidly connected to the descender. The nozzle may have an outlet for discharging fluidic droplets, which may be formed on the outer substrate surface. A recycle passage may be formed in the substrate and fluidly connected to the descender, and the recycle passage may not be fluidly connected to different fluid pumping chambers. The nozzle may have an opening opposite the outlet and a tapered portion between the nozzle opening and the outlet. The surface of the recirculation passage proximate the nozzle may be substantially flush with the nozzle opening.

In another embodiment, a fluid droplet dispensing device includes a substrate having a fluid pumping chamber formed therein, a descender formed in the substrate and fluidly connected to the fluid pumping chamber, and a fluid formed in the substrate and fluidly connected to the descender and coplanar with the outer substrate surface. And a nozzle having a droplet outlet. In addition, two recycling passages can be symmetrically disposed around and fluidly connected to each descender.

In another embodiment, the fluid droplet dispensing apparatus may include a substrate having a fluid pumping chamber formed therein, a descender formed in the substrate and fluidly connected to the fluid pumping chamber, and a nozzle formed in the substrate and fluidly connected to the descender. The actuator may be in pressure communication with the fluid pumping chamber and may generate a firing pulse having a firing pulse frequency to eject fluid droplets from the nozzle. The recycle passage may be formed in the substrate and configured to have an impedance at a firing pulse frequency that is substantially higher than the impedance of the nozzle.

In another embodiment, a fluid droplet ejection device includes a substrate in which a fluid pumping chamber is formed, an actuator in pressure communication with the fluid pumping chamber and capable of generating a firing pulse having a firing pulse width to eject the droplet from the nozzle, and a substrate And a descender formed in and fluidly connected to the fluid pumping chamber. The nozzle may be formed in the substrate and fluidly connected to the descender. A recycle passage can be formed in the substrate and fluidly connected to the descender, the recycle passage having a length substantially equal to the firing pulse width multiplied by the speed of sound in the two separate fluids.

Embodiments may include one or more of the following features. The pump may be configured to maintain a predetermined height difference between the fluid height in the fluid supply tank and the fluid height in the fluid return tank, the predetermined height difference attracting bubbles or contaminants through the fluid pumping chamber, the descender, and the recirculation passage. It may be selected to generate a flow of fluid through the substrate at a flow rate sufficient to produce it. The system may consist of a pump that is not fluidly connected between the substrate and the fluid supply tank. The system may also be comprised of a pump that is not fluidly connected between the substrate and the fluid return tank. The ratio of the flow rate (expressed in picolites per second) to the area of the outlet (expressed in square microns) through the recycle passage may be approximately 10 or greater. In some embodiments, the area of the exit can be approximately 156 square microns and the flow rate through the recycle passage can be at least 1500 picoliters per second. The distance between the outer substrate surface and the closest surface of the recycle passage may be less than approximately 10 times the outlet width. In some embodiments, the outlet width can be approximately 12.5 microns and the distance between the outer substrate surface and the nearest surface of the recycle passage can be less than approximately 60 microns. The system can further include a degasser positioned to remove air from the flow of fluid through the substrate. In addition, the system can further include a filter positioned to remove contaminants from the flow of fluid through the substrate. In addition, the system may further include a heater positioned to heat the flow of fluid through the substrate.

In addition, two recirculation passages can be configured such that fluid can flow from the descender to each of the two recirculation passages. Two recirculation passages are configured such that fluid can flow from one of the two recirculation passages through the descender to the other of the two recirculation passages. The dimensions of the two recirculation passages may be approximately equal to each other.

In some embodiments, only a single recycle passage is fluidly connected to each descender. The impedance of the recirculation passage at the firing pulse frequency may be at least two times higher than the impedance of the nozzle and at least ten times higher than the impedance of the nozzle. The impedance of the recirculation passage at the firing pulse frequency can be high enough to prevent energy loss from the firing pulse through the recirculation passage, which significantly drops the pressure applied to the fluid at the nozzle. The firing pulse frequency may have a firing pulse width and the length of the recirculation passage may be substantially the same as the firing pulse width multiplied by the speed of sound in two separate fluids. The cross-sectional area of the recycle passage may be smaller than the cross-sectional area of the descender and may be less than approximately 1/10 of the cross-sectional area of the descender. The apparatus may also include a recycle channel formed in the substrate and in fluid communication with the recycle passage, and the transition of the cross-sectional area between the recycle passage and the recycle channel may comprise an acute angle.

In some embodiments, the device may include one or more of the following advantages. Circulating fluid close to the nozzle and outlet can prevent contaminants from interfering with fluid droplet discharge and prevent ink from drying out of the nozzle. Circulation of the removed fluid may remove the fluid supplied from the hydraulic pressure and remove or dissolve bubbles. If the device includes a plurality of nozzles, the removal of bubbles and supplied ink may promote uniform fluid droplet discharge. In addition, the use of a high impedance recycle passage at the firing pulse frequency can minimize the energy lost through the recycle passage and reduce the time required to refill the nozzle after fluid droplet discharge. In addition, the uniform arrangement of the recirculation passages for each nozzle can facilitate proper alignment of the nozzles. Symmetrical placement of the recirculation passage around the nozzle can reduce or eliminate deflection of fluid droplets that can otherwise be caused by the provision of a single recirculation passage or recirculation passages that are not symmetrically disposed around the nozzle. The system may be self-contained. In addition, a system having a fluid supply tank and a fluid return tank and a pump between these tanks facilitates the release of fluid without pressure pulses normally caused by the pump by separating the pressure effect of the pump from the rest of the system, such as the flow path body. can do.

The details of one or more embodiments of the invention are defined in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

1A is a side cross-sectional view of a portion of a printhead.
FIG. 1B is a top cross-sectional view taken along the BB line of FIG. 1A and seen in the direction of the arrow. FIG.
FIG. 1C is a top cross-sectional view taken along the CC line of FIG. 1A and seen in the direction of the arrow. FIG.
FIG. 2 is a side cross-sectional view taken along the line 2-2 of FIG. 1B and seen in the direction of the arrow. FIG.
3A is a side cross-sectional view of another embodiment of a fluid discharge structure.
FIG. 3B is a cross-sectional plan view taken along the line 3-3 of FIG. 3A and seen in the direction of the arrow.
4 is a plan sectional view of another embodiment of a fluid discharge structure.
5 is a cross-sectional plan view taken along the line 5-5 of FIG. 2 and viewed in the direction of the arrow.
6 is a schematic diagram of a system for fluid recirculation.
7A is a graph showing firing pulses.
FIG. 7B is a graph showing the pressure in response to the firing pulse shown in FIG. 7A.

Like reference numerals in the drawings denote like elements.

Fluid droplet ejection may be effected by a substrate comprising a fluid flow path body, a membrane, and a nozzle layer. The flow passage body is formed with a fluid flow passage that may include a fluid pumping chamber, a descender, a nozzle having an outlet, and a recirculation passage. The fluid flow path may be microfabricated. The actuator may be located on the surface of the membrane opposite the flow path body and proximate the fluid pumping chamber. When the actuator is actuated, the actuator applies a firing pulse to the fluid pumping chamber to discharge fluid droplets through the outlet. The recirculation passage may be fluidly connected to the nozzle and the outlet, for example a descender flush with the nozzle. Fluid can be circulated constantly through the flow path and fluid not exiting the outlet can be sent through the recirculation passage. Frequently, the flow passage body includes a plurality of fluid flow passages and nozzles.

The fluid droplet ejection system can include a substrate. The system may also include a fluid source for the substrate as well as a return for fluid that flows through the substrate but does not exit the nozzle of the substrate. The fluid reservoir may be fluidly connected to a substrate for supplying fluid, such as ink, to the substrate for discharge. Fluid flowing from the substrate can be sent to a fluid return tank. The fluid can be, for example, a chemical compound, a biological material, or an ink.

Referring to FIG. 1A, a cross-sectional schematic view of a portion of a printhead 100 in one embodiment is shown. The printhead 100 includes a substrate 110. The substrate 110 includes a flow path body 10, a nozzle layer 11, and a membrane 66. The substrate inlet 12 supplies fluid to the fluid inlet passage 14. The fluid inlet passage 14 is fluidly connected to the riser 16. The riser 16 is fluidly connected to the fluid pumping chamber 18. The fluid pumping chamber 18 is in close proximity to the actuator 30. The actuator 30 may include a piezoelectric layer 31, such as lead zirconium titanate (PZT), an electrical trace 64, and a ground electrode 65. A voltage is applied between the electrical trace 64 and the ground electrode 65 of the actuator 30 and actuates the actuator 30 by applying a voltage to the actuator 30. The membrane 66 is between the actuator 30 and the fluid pumping chamber 18. The attachment layer 67 secures the actuator 30 to the membrane 66. As continued in FIG. 1A, although the actuator 30 is shown, the piezoelectric layer 31 may be produced discontinuously, for example, by an etching step or the like during fabrication. Further, although FIG. 1A illustrates various passages, such as the recirculation passage and the inlet passage, and the substrate inlet 12, these components may not all be in common (the embodiments illustrated in FIGS. 1B and 1C). Not in common with). In some embodiments, two or more of the flow passage body 10, the nozzle layer 11, and the membrane may be formed in one piece.

The nozzle layer 11 is fixed to the bottom of the flow passage body 10. A nozzle 22 having an outlet 24 is formed on the outer nozzle layer surface 25 of the nozzle layer 11. The fluid pumping chamber 18 is fluidly connected to the descender 20 fluidly connected to the nozzle 22 (see FIG. 2). Fluid pumping chamber 18, descender 20, and nozzle 22 may be referred to collectively as a fluid pressure path here. For the square shaped outlet 24, the length of the outlet 24 side may be between about 5 microns and about 100 microns, such as about 12.5 microns, for example. If the outlet 24 is other than square, the average width may be between about 5 microns and about 100 microns, such as about 12.5 microns, for example. This outlet size can produce a useful fluid droplet size for some embodiments.

The recirculation passage 26 is fluidly connected to the descender 20 at a position near the nozzle 22, as described in more detail below. In addition, the recirculation passage 26 is fluidly connected to the recirculation channel 28 to extend between the descender 20 and the recirculation channel 28. In addition, the recycle channel 28 may have a larger cross-sectional area than the recycle passage 26, and the change in cross-sectional area may be rather rapid rather than gradual. Sudden changes in cross-sectional area may facilitate minimizing energy loss through the recirculation passage 26, as described in more detail below. In addition, the recirculation passage 26 may have a smaller cross-sectional area than the descender 20. For example, the cross-sectional area of the recirculation passage 26 may be less than 1/10 of the cross-sectional area of the descender 20, or may be less than 1/100. Other features in the riser 16, the fluid pumping chamber 18, the descender 20, the recirculation passage 26, and the substrate may be microfabricated in some embodiments.

FIG. 1B is an exemplary cross-sectional view of a portion of the printhead 100 taken along the B-B line of FIG. 1A. 1C is an exemplary cross-sectional view of a portion of the printhead 100 taken along the C-C line of FIG. 1A. 1B and 1C, the passage body 10 is provided with a plurality of inlet passages 14 extending in parallel with each other. The plurality of inlet passages 14 are in fluid communication with the substrate inlet 12. In addition, the passage body 10 is formed with a plurality of recirculation channels 28 in fluid communication with the substrate outlet (not shown). In addition, the flow passage body 10 includes a plurality of risers 16, a fluid pumping chamber 18, and a descender 20 formed therein. The riser 16 and the fluid pumping chamber 18 extend in parallel patterns in different patterns, and the descender 20 also extends in parallel columns. Each riser 16 is shown in fluid connection with an inlet passage 14 to a corresponding fluid pumping chamber 18, and each fluid pumping chamber 18 is shown in fluid connection to a corresponding descender 20. have. Recirculation passages 26 formed in the flow passage body 10 fluidly connect each descender 20 to one or more corresponding recirculation channels 28. Referring to FIG. 1C, each descender 20 is shown having a corresponding nozzle 22. Each column of the fluid pressure path may be fluidly connected to the common inlet passage 14, and each fluid pressure path may have its own recirculation passage 26 separated from the other fluid pressure path. This arrangement can provide a uniform flow of fluid in the same direction through each fluid pressure path (including through the recirculation passage 26) connected to the common inlet passage 14. This can prevent fluid discharge fluctuations caused, for example, by having a recirculation passage connected to adjacent fluid pressure paths (eg, add and even pressure paths). In some embodiments, the plurality of flow path portions each comprising a fluid pumping chamber 18, a lowerer 20, and a recirculation passage 26 are in fluid between the fluid inlet passage 14 and the recirculation channel 28 in parallel. Connected. That is, the plurality of flow path portions may be configured to have no fluid connection with each other (eg, except through the fluid inlet passage 14 or the recirculation channel 28). In some embodiments, each flow passage portion may also include a riser 16.

2 is an exemplary cross-sectional diagram cut along the line 2-2 of FIG. 1B. The fluid inlet passage 14, the riser 16, the fluid pumping chamber 18, the descender 20, the nozzle 22, and the outlet 24 are arranged similarly to FIG. 1A. Attachment layer 67 is not shown for simplicity. Recirculation passage 26 has passage surface 32 closest to outer nozzle layer surface 25. The distance D between the outer nozzle layer surface 25 and the passage surface 32 is less than about 10 times the width of the outlet 24, for example between about 2 times and about 10 times the width of the outlet 24, for example Approximately between 4.4 and 5.2 times, for example, 4.8 times the width of the outlet 24 (or the average width of the outlet 24 if the outlet 24 is other than square). For example, for an exit 24 having a width of 12.5 microns, the distance D may be approximately 60 microns or less. The recirculation passage 26 may be further away from the outlet 24 as the outlet 24 becomes larger. Proximity between the recirculation passage 26 and the outlet 24 may facilitate removal of contaminants near the outlet 24, as described in more detail below. As another example, the nozzle 22 can be tapered in shape and the passage surface 32 can be flush with the boundary of the nozzle 22 opposite the outlet 24. That is, the passage surface 32 may be immediately adjacent to the taper of the nozzle 22 and may be, for example, flush with the nozzle. 2 also shows that the recirculation passage 26 has a length L between the descender 20 and the recirculation channel 28. The length L may be selected to minimize energy loss through the recirculation passage 26, as described below. In some embodiments, the passage surface may be close to the taper of the nozzle 22 but separated by a small distance, such as between about 5 microns and about 10 microns, to account for manufacturing constraints.

3A is an exemplary cross-sectional view of a portion of another flow passage body 10 '. The adhesion layer 67 is not shown for simplicity. The fluid inlet passage 14, the riser 16, the fluid pumping chamber 18, the descender 20, the nozzle 22, and the outlet 24 are arranged in a manner similar to the arrangement shown in FIG. 2. However, the two recirculation passages 26A, 26B are fluidly connected to the descender 20. Each of the two recirculation passages 26A, 26B is fluidly connected to the corresponding recirculation channels 28A, 28B. Two recirculation passages 26A, 26B are arranged on opposite sides of the nozzle 22, which arrangement may be symmetrical with respect to the descender 20. That is, the recirculation passages 26A, 26B are axially aligned with each other through the center of the descender 20. In some embodiments, recirculation passages 26A and 26B may be the same cross-sectional size and the same length with respect to each other.

3B is an exemplary cross sectional view along line 3-3 of FIG. 3A. Square shaped nozzles 22 and outlets 24 are shown, as are the fluid inlet passages 14 and recirculation channels 28A and 28B. Recirculation passages 26A and 26B are symmetrically disposed about an axis through the center of the nozzle 22.

Figure 4 illustrates a portion of another alternative embodiment of the flow passage body 10 ". Two recycling passages 26 'are fluidly connected to the descender 20. The recycling passage 26' shown in Figure 4 is shown. Is fluidly connected to the common recycle channel 28. Although the recycle passage 26 'is shown as being squared-off at right angles in Figure 4, the recycle passage 26' is shown in Figure 1C as shown. It may be formed as a curve or a series of curves for the recycling passage (26).

This embodiment can be used for a series of nozzles 22 and outlets 24, and FIG. 5 shows two nozzles (in the embodiment with one recycle passage 26, in which each nozzle 22 extends therefrom. 22) and outlet 24 are illustrated. As described above with reference to FIG. 2, some embodiments provide a recirculation passage 26 for each nozzle 22 disposed on the same side of the corresponding nozzle, respectively, relative to the recirculation passage 26 corresponding to the other nozzle 22. Has That is, each recirculation passage 26 for the nozzle 22 in the row or column of the nozzle 22 may extend from the nozzle 22 in the same direction. 5 shows an embodiment with an arrangement of recirculation passages 26 extending all from the same side of multiple nozzles 22. Such a uniform arrangement may facilitate uniformity of fluid droplet discharge among the plurality of nozzles 22. Without being limited to any particular theory, the uniformity of fluid droplet discharge characteristics, such as discharge direction, is easy because the effect of the recirculation passage 26 on the pressure in the fluid pressure path is approximately the same for all of the nozzles 22. Thus, any pressure change or high pressure spot caused by the presence of the recirculation passage 26 causes the discharged fluid droplets to deflect in the direction away from the normal to the outer nozzle layer surface 25 and the effect is exerted on all the nozzles 22. Is the same for. In some embodiments, multiple recycle passages 26 may be fluidly connected to common recycle channel 28.

Referring to FIG. 6, the printhead 100 described above is connected to an embodiment of a fluid pumping system. Only a portion of the printhead 100 is shown for simplicity. Recirculation channel 28 is fluidly connected to fluid return tank 52. Fluid reservoir 62 is fluidly connected to reservoir pump 58 that controls fluid height in fluid return tank 52, which may be referred to as return height H1. The fluid return tank 52 is fluidly connected to the fluid supply tank 54 by the supply pump 59. Feed pump 59 controls the fluid height in fluid supply tank 54, which may be referred to as supply height H2. Alternatively, in some embodiments, feed pump 59 may be configured to maintain a predetermined height difference between return height H1 and feed height H2. Return height H1 and feed height H2 are measured with respect to a common reference level as shown by the broken line between fluid return tank 52 and fluid supply tank 54 in FIG. 6. Fluid supply tank 54 is fluidly connected to fluid inlet channel 14. In some embodiments, the pressure at nozzle 22 may be kept slightly lower than the atmosphere, which may prevent or mitigate fluid leakage or fluid drying. This is achieved by having the fluid level of the fluid return tank 52 and / or fluid supply tank 54 under the nozzle 22, or by a vacuum pump of the fluid return tank 52 and / or fluid supply tank 54. This can be achieved by reducing the air pressure over the surface. Fluid connections between components in the fluid pumping system may include rigid or flexible tubing.

The degasser 60 may be fluidly connected between the fluid supply tank 54 and the fluid inlet passage 14. Alternatively, the degasser 60 may be connected between the recirculation channel 28 and the fluid return tank 52, between the fluid return tank 52 and the fluid supply tank 54, or at any other suitable location. have. The degassers 60 may remove bubbles and decomposed air from the fluid, for example the degassers 60 may remove fluids. Fluid leaving the degassers 60 may be referred to as removed fluid. The degasser 60 may be a vacuum type such as the SuperPhobic® Membrane Contactor available from Membrana of Charlotte, North Carolina. Optionally, the system may include a filter for removing contaminants from the fluid (not shown). The system may also include a heater (not shown) or other temperature control device to maintain the fluid at the desired temperature. The filter and heater may be fluidly connected between the fluid supply tank 54 and the fluid inlet passage 14. Alternatively, the filter and heater may be fluidly connected between the recirculation channel 28 and the fluid return tank 52, between the fluid return tank 52 and the fluid supply tank 54, or any other suitable location. In addition, a makeup part (not shown) may optionally be provided to monitor, control, and / or adjust the properties or composition of the fluid. Such makeup may be desirable, for example, if the evaporation of the fluid (eg, long periods of no use, limited use, or intermittent use) can change the viscosity of the fluid. The makeup part may, for example, monitor the viscosity of the fluid, and the makeup part may add a solvent to the fluid to achieve the desired viscosity. The makeup may be fluidly connected between the fluid supply tank 54 and the printhead 100, between the fluid return tank 52 and the fluid supply tank 54, within the fluid supply tank 54, or at any other suitable location. Can be.

In operation, fluid reservoir 62 supplies fluid to reservoir pump 58. The reservoir pump 58 controls the return height H1 in the fluid return tank 52. The feed pump 59 controls the feed height H2 in the fluid supply tank 54. The height difference between the supply height H2 and the return height H1 is the fluid through the degasser 60, the printhead 100, and any other component connected between the fluid supply tank 54 and the fluid return tank 52. Flow of the fluid may be generated without pumping the fluid directly to or from the printhead 100. That is, there is no pump between the fluid supply tank 54 and the printhead 100 or between the printhead 100 and the fluid return tank 52. Fluid from the fluid supply tank 54 flows through the degassers 60, through the substrate inlet 12 (FIG. 1), and into the fluid inlet passage 14. From the fluid inlet passage 14, fluid flows through the riser 16 and into the fluid pumping chamber 18. The fluid then flows through the descender 20 and into either the outlet 24 or the recirculation passage 26. Most of the fluid flows from the region near the nozzle 22 through the recirculation passage 26 and into the recirculation channel 28. From the recirculation channel 28, fluid may be refluxed to the fluid return tank 52.

When one or more nozzles 22 and outlets 24 are used in the droplet ejection apparatus, as in the embodiment shown in FIG. 5, the flow of fluid may be in the same direction of each of the recirculation passages 26. The uniformity of flow direction between the nozzles can enhance the uniformity of fluid droplet ejection characteristics between the nozzles 22. Fluid droplet discharge characteristics include, for example, droplet size, discharge velocity, and discharge direction. Without being limited to any particular theory, the uniformity of the discharge characteristics can be attributed to the uniformity of any pressure effect caused by the flow of fluid near the nozzle 22. In the case where each nozzle 22 is provided with two or more recirculation passages 26A and 26B, as in the embodiment shown in FIGS. 3A and 3B, the flow direction of the fluid is the nozzles of the recirculation passages 26A and 26B. Can be separated from (22). Alternatively, fluid may flow from one recycle passage 26A to the other recycle passage 26B. Similarly, in the embodiment shown in FIG. 4, the flow direction of the fluid can be spaced apart from the nozzles 22 of both recirculation passages 26 ′.

The presence of the recirculation passage 26 may rather occur at an angle that results in droplet discharge from the outlet 24 and orthogonal to the outer nozzle layer surface 25. Without being limited to any particular theory, this deflection may arise from pressure imbalances near the nozzle 22 caused by the flow of fluid through the recirculation passage 26. When one or more nozzles 22 and outlets 24 are used, the recirculation passages 26 of each nozzle are recirculating passages 26 on the same side of each nozzle 22, as shown in FIG. 5. Any effect of the presence of may be the same for each nozzle. The discharge from the nozzle 22 is uniform because any effect is the same for each nozzle. In the case where each nozzle has two recycling passages 26A and 26B, as shown in FIG. 4, the recycling passages 26A and 26B may be symmetrically disposed around the nozzle 22. Without being limited to any particular theory, the symmetrical arrangement of the recycling passages 26A, 26B can produce the same and opposite effects that cancel each other out.

The flow of removed fluid near the nozzle 22 can prevent drying of the fluid near the outlet 24 where the fluid is typically exposed to air. It may also remain from the bubble and supplied priming, or may enter through an outlet 24 or other location. Bubbles and their effects in fluid droplet ejection systems are discussed in more detail below. In some embodiments, the fluid flowing through the fluid inlet passage 14 is at least partially removed with bubbles and broken down into air by the degassers 60. The flow of supplied fluid near the nozzle 22 can remove bubbles and supplied fluid near the nozzle 22 and outlet 24 by replacing the supplied fluid with the removed fluid. If the fluid is ink, the agglomeration of the ink or pigment may form when the ink does not flow or is exposed to air. The flow of fluid may eliminate agglomeration of ink or pigment from the flow path body that interfaces differently from fluid droplet discharge and serves as nucleation sites for bubbles. In addition, the flow of the fluid can reduce or prevent the fixation of the pigment of the ink.

In some embodiments, the flow rate through the recirculation passage 26 may be high enough to mitigate or prevent the fluid from drying near the outlet 24. The evaporation rate of the fluid near the outlet 24 is proportional to the area of the outlet 24. For example, the evaporation rate of the fluid can be doubled if the area of the outlet 24 is doubled. The numerical magnitude of the flow rate through the recirculation passage 26, expressed in picolites per second, to mitigate or prevent the drying of the fluid when the system is operating, is in some embodiments of the area of the outlet 24 expressed in square microns. One or more times (eg, two or more, five or more, or ten or more) greater than the numerical size. The flow rate also depends on the type of fluid used. For example, if the fluid is a fluid that dries relatively quickly, then the flow rate can be increased to compensate for it, and conversely the flow rate can be slow for fluids that are dried relatively slowly. For example, for a square shaped outlet 24 measuring 12.5 microns on each side, the flow rate may be at least 1500 picoliters per second (eg, at least 3000 picoliters per second). This flow rate may be an order of magnitude, such as 10 times or more, than the flow rate required to provide a suitable fluid to exit through the outlet 24 during normal fluid droplet discharge. However, this flow rate may be much smaller than the flow rate at the maximum operating frequency. For example, if the maximum fluid droplet discharge frequency is 30 kHz and the volume of each drop ejected is 5 picoliters, then the flow rate at the maximum operating frequency is approximately 150,000 picoliters per second. The flow of removed fluid may pass close to the nozzles 22 and 24 as discussed with reference to FIG. 5 above. The flow rate just described can prevent drying of the fluid and can sweep bubbles, debris, and other contaminants that can otherwise settle in the nozzle 22 at low flow rates.

Recirculation of the fluid may be required differently, such as by using an external device to drain the fluid, inhaling bubbles and supplied fluid from the nozzle 22, or drawing or otherwise drawing air from the nozzle 22 differently. Reduce or eliminate the need to perform various purging or cleaning activities. Such a technique requires an external device to interface with the nozzle 22 to prevent droplet deposition and reduce productivity. Instead, the above-described flow of fluid supplied in close proximity to the nozzle 22 can remove bubbles and supplied fluid without requiring an external device to interface with the nozzle 22. Therefore, when the fluid is empty in the flow passage body 10, for example, when the above-mentioned system is first empty with the fluid, the system can be "self primed" by flowing the fluid through the flow passage body 10. That is, in some embodiments, the system may purge air from the flow path body 10 instead of or in addition to drawing or drawing air from the nozzle 22.

The flow of fluid described above may not be sufficient for fluid to exit the outlet 24 in some embodiments. Actuators, such as piezoelectric transducers or resistance heaters, may be provided adjacent to the fluid pumping chamber 18 or the nozzle 24 to achieve droplet ejection. Actuator 30 may include a piezoelectric layer 31, such as a lead zirconium titanate (PZT) layer. The electrical voltage applied to the piezoelectric layer 31 can cause the layer to change in shape. If the membrane 66 (see FIG. 1) between the actuator 30 and the fluid pumping chamber 18 can be moved due to the piezoelectric layer 31 changing in shape, then the electrical applied across the actuator 30 is then applied. The voltage can cause a change in the volume of the fluid pumping chamber 18. This change in volume can produce a pressure pulse, referred to herein as a firing pulse. The firing pulse may result in a pressure wave propagating through the descender 20 to the nozzle 22 and the outlet 24. Accordingly, the firing pulse can result in the discharge of fluid from the outlet 24.

Bubbles are typically much more compressible than fluids circulating through the system described above. Therefore, bubbles may absorb a substantial amount of energy of the firing pulse when present in the fluid pumping chamber 18, the descender 20, or the nozzle 22. If a bubble is present, this volume change may be absorbed at least in part by the compression of the bubble instead of the volume change of the fluid pumping chamber 18 which would result in a proper amount of fluid discharge through the nozzle 22. This may result in insufficient pressure at the nozzle 22 to cause the discharge of the fluid droplet through the outlet 24, or allow the droplet to be discharged less than the desired droplet, or so that the droplet can be discharged slower than the desired rate. Can cause A large electrical voltage may be applied to the actuator 30 or a large fluid pumping chamber 18 may be used to provide sufficient energy to achieve more complete fluid droplet discharge, but the size and energy requirements of the system components are increased. In addition, the presence of many bubbles in some fluid pressure paths as compared to others where the device includes multiple nozzles can cause non-uniformity of fluid droplet discharge from the nozzle to the nozzle.

Flowing the removed fluid through the fluid pressure path may remove bubbles and supplied fluid. The supplied fluid, ie, the fluid containing the decomposed air, is easier to bubble than the removed fluid. Thus, the removal of the supplied fluid can help to reduce or eliminate the presence of bubbles. As discussed above, reducing or eliminating the presence of bubbles can help minimize the electrical voltage that must be applied to the actuator 30. The required size of the fluid pumping chamber 18 can likewise be minimized. In addition, inconsistencies in droplet ejection among multiple nozzles due to the presence of bubbles can be reduced or eliminated.

Although having a recirculation passage 26 fluidly connected to the descender 20 may facilitate removal of bubbles or other contaminants, the recirculation passage 26 may reduce the energy applied by the actuator 30. To provide a path. This energy loss damages the pressure applied to the fluid at nozzle 22 and outlet 24. If this energy loss impairs the applied pressure then a large electrical voltage may be required to be applied to the actuator 30 at this time or a large fluid pumping chamber 18 may need to be provided for sufficient energy to reach the nozzle 22. have. By designing the recirculation passage 26 with an impedance that is much higher than the impedance of the descender 20 and the nozzle 22 at the firing pulse frequency, it is necessary for less energy to compensate for the energy loss through the recirculation passage 26. For example, the impedance of the recirculation passage 26 may be greater than the descender 20 and the nozzle 22, such as at least 2 times, at least 5 times, or at least 10 times.

Impedances higher than the impedances of the downcomer 20 and the nozzle 22 can be partially achieved by providing a recirculation passage 26 having a cross-sectional area smaller than the cross-sectional area of the downcomer 20. In addition, the abrupt change in impedance between the recirculation passage 26A and the recirculation channel 28 can facilitate the reflection of pressure pulses in the recirculation passage 26. The recirculation channel 28 may have a lower impedance than the recirculation passage 26, and the change in impedance between the recirculation passage 26A and the recirculation channel 28 may be abrupt to minimize reflection of the pressure pulse. For example, a sudden change in impedance may be caused by an acute angle, such as a right angle, in the transition between recycle passage 26A and recycle channel 28. Sudden changes in impedance can result in the reflection of pressure pulses that change the cross-sectional area at the boundary between the recirculation passage 26A and the recirculation channel 28.

7A shows a graph of the voltage applied across actuator 30 over time. The bias voltage Vb is present over the actuator 30 when the actuator 30 is not fired. 7B shows a pressure graph in the fluid pumping chamber 18 over time. Referring to FIG. 7A, the firing pulse has a firing pulse width (W). This firing pulse width W is the length of time roughly defined by the drop in voltage to low voltage Vo and the dwell at low voltage Vo. Circuitry (not shown) in electrical communication with the actuator 30 may include a driver configured to control the shape of the firing pulse, including the firing pulse frequency, and the size of the firing pulse width W. FIG. The circuit can also control the timing of firing pulses. The circuit may be automatic or may be manually controlled, for example by a computer with computer software configured to control fluid droplet discharge, or by some other input. In another embodiment, the firing pulse may not include a bias voltage Vb. In some embodiments, the firing pulse may include an increase in voltage, an increase and decrease in voltage, and any other alteration of voltage.

Referring to FIG. 7B, the firing pulse causes a pressure variation in the fluid pumping chamber 18 by a frequency corresponding to the firing pulse frequency. First, the pressure in the fluid pumping chamber 18 drops below the normal pressure Po for a period corresponding to the firing pulse width W. Then, the pressure in the fluid pumping chamber 18 is reduced to normal pressure Po by decreasing the amplitude until the pressure in the fluid pumping chamber returns to normal pressure Po or until the actuator 30 applies pressure again. Fluctuates higher and lower. The amount of time during which the pressure is higher than the normal pressure Po and lower during each variation of pressure in the fluid pumping chamber 18 corresponds to the firing pulse width W. FIG. The firing pulse width W may be a specific flow path design (e.g., dimensions of the fluid pressure path, such as the size of the pumping chamber 18, or whether the flow path comprises the riser 16 or the descender 20) and / or discharge. You can depend on the drop volume being created. For example, since the size of the pumping chamber is reduced, the resonance frequency of the pumping chamber may be increased, thereby reducing the width of the firing pulse. For a pumping chamber that discharges approximately 2 picoliters of drop volume, the pulse width W may be, for example, between approximately 2 microseconds and 3 microseconds, and the pumping chamber ( 18, the pulse width W may be between about 10 and about 15 microseconds.

The length L of the recirculation passage 26 (see FIG. 2) is such that the time required for the pressure pulse traveling at twice the length L at the speed of sound c of the fluid is approximately equal to the firing pulse width W. FIG. Can be configured. This relationship can be expressed as:

If the fluid is ink, the speed of sound (c) is usually approximately 1100-1700 m / s. If the firing pulse width W is between about 2 microseconds and about 3 microseconds, the length L may be about 1.5 millimeters to about 2.0 millimeters.

Selecting a length L that satisfies the relationship may provide a higher impedance to the recirculation passage 26 than if L does not satisfy this relationship. Selecting the length L that satisfies the relationship, without being bound to any particular theory, requires that the pressure drop 20 from the actuator 30 propagating down the recirculation passage 26 reinforce the firing pulse. To be reflected again.

Also, as discussed above, selecting the length L can reduce the resistance to refill the fluid 22 with the nozzle 22. Upon refilling the nozzle 22, a meniscus is formed at the outlet 24. During and after the refilling of the nozzle 22 the shape of this meniscus is altered or varied, resulting in a partial mismatch in the direction of fluid droplet discharge. As mentioned above, selecting the length L can improve refilling of the nozzle 22 and reduce the required amount of meniscus settling time. Reducing the amount of time required to stabilize the meniscus can reduce the amount of settling time required between fluid droplet discharge. Thus, with the proper length L of the recirculation passage 26, fluid droplet discharge can occur at a high rate, that is, with a lot of discharge over a period of time, which may also be referred to as high frequency.

The above-described embodiments can provide none, some or all of the following advantages. Recirculation of fluid close to the nozzle and outlet may prevent drying of the fluid and the accumulation of contaminants that may interface with fluid droplet discharge. Circulation of the removed fluid can clean the fluid supplied from the fluid pressure path and remove or dissolve bubbles. High flow rates of the fluid can assist in moving, removing and preventing the accumulation of small bubbles and other contaminants. When the fluid is an ink with a pigment, the high flow rate of the fluid can prevent the pigment from settling or agglomerating. Removal of the bubble and the supplied fluid may prevent the bubble from absorbing energy from the firing pulse. Where the device comprises a plurality of noses, the absence of bubbles and supplied fluid can promote uniform fluid droplet discharge. In addition, using a recycle passage with high impedance at the firing pulse frequency minimizes the energy lost through the recycle passage. Thus, high efficiency can be obtained. Proper selection of the length of the recirculation passage can reduce the meniscus settling time and reduce the time required to refill the nozzle after fluid droplet discharge. In addition, the uniform arrangement of the recirculation passages for each nozzle can enhance the uniformity of fluid droplet discharge to facilitate proper alignment of the nozzles. In an alternate embodiment, the symmetrical arrangement of the recycle passages can reduce or eliminate the deflection of the discharge direction, thereby eliminating any drop discharge timing compensation or other compensation requirements. The system described above may be self-priming. In addition, a system with a fluid supply tank and a fluid return tank and a pump between these tanks can separate the pressure effect of the pump from the rest of the system to facilitate the discharge of fluid without the pulse pressure normally caused by the pump.

Although the invention has been described herein with reference to specific embodiments, other features, objects, and advantages of the invention will be apparent from the description and drawings. All such modifications are included within the intended scope of the present invention as defined in the following claims.

Claims (34)

A fluid pumping chamber, a descender fluidly connected to the fluid pumping chamber, a nozzle arranged to discharge fluid droplets through an outlet fluidly connected to the descender and formed on an outer nozzle layer surface, and in fluidic contact with the lowering pumping chamber A substrate comprising a flow path body having a flow path including a recirculation passage closer to the nozzle;
A fluid supply tank fluidly connected to the fluid pumping chamber;
A fluid return tank fluidly connected to the recirculation passage; And
Fluidly connected to the fluid return tank and the fluid supply tank to form a flow path from the fluid supply tank to the substrate and through the substrate, from the substrate to the fluid return tank, and from the fluid return tank to the fluid supply tank. And a pump configured to cause the fluid droplet discharge system. The method of claim 1,
The pump is configured to maintain a predetermined height difference between the fluid height in the fluid supply tank and the fluid height in the fluid return tank, the predetermined height difference being bubbled through the fluid pumping chamber, the descender, and the recirculation passage. Or to generate a flow of fluid through the substrate at a flow rate sufficient to draw off contaminants. The method of claim 1,
And no pump is fluidly connected between the substrate and the fluid supply tank. The method of claim 1,
And no pump is fluidly connected between the substrate and the fluid return tank. The method of claim 1,
And a ratio of the flow rate (expressed in picolites per second) to the outlet area (expressed in square microns) passing through the recirculation passage is approximately 10 or greater. The method of claim 5, wherein
And the outlet area is approximately 156 square microns and the flow rate through the recirculation passage is approximately 1500 picoliters or more per second. The method of claim 1,
And the distance between the outer substrate surface and the nearest surface of the recirculation passage is less than approximately 10 times the outlet width. The method of claim 7, wherein
The outlet width is approximately 12.5 microns, and the distance between the outer substrate surface and the nearest surface of the recycle passage is less than approximately 60 microns. The method of claim 1,
And a degasser positioned to remove air from the flow of fluid through the substrate. The method of claim 1,
And a filter positioned to remove contaminants from the flow of fluid through the substrate. The method of claim 1,
And a heater positioned to heat the flow of fluid through the substrate. A substrate on which a fluid pumping chamber is formed;
A descender formed in the substrate and fluidly connected to the fluid pumping chamber;
An actuator in pressure communication with the fluid pumping chamber;
A nozzle formed in said substrate, fluidly connected to said descender, said nozzle having a fluid droplet outlet formed on a surface of an outer substrate; And
A distance between the outer substrate surface and the closest surface of the recirculation passage is formed in the substrate at a position no greater than approximately 10 times the outlet width, the recirculation passage being fluidly connected to the descender and not fluidly connected to a different fluid pumping chamber. Fluid droplet dispensing apparatus comprising a. The method of claim 12,
The outlet width is approximately 12.5 microns and the distance between the outer substrate surface and the nearest surface of the recirculation passage is approximately 60 microns or less. The method of claim 12,
And a ratio of flow rate (expressed in picolites per second) to the outlet area (expressed in square microns) passing through the recirculation passage is approximately 10 or greater. The method of claim 14,
And said outlet area is approximately 156 square microns and the flow rate through said recirculation passage is approximately 1500 picoliters per second or more. A substrate on which a fluid pumping chamber is formed;
A descender formed in the substrate and fluidly connected to the fluid pumping chamber;
An actuator in pressure communication with the fluid pumping chamber;
A nozzle formed in said substrate, fluidly connected to said descender, said nozzle having a fluid droplet outlet formed on an outer substrate surface; And
A fluid droplet ejection device comprising a recirculation passage formed in said substrate and fluidly connected to said descender and not fluidly connected to a different fluid pumping chamber:
The nozzle has a nozzle opening opposite the outlet and a tapered portion between the nozzle opening and the outlet;
And the surface of the recirculation passage proximate to the nozzle is substantially flush with the nozzle opening. A substrate on which a fluid pumping chamber is formed;
A descender formed in the substrate and fluidly connected to the fluid pumping chamber;
A nozzle formed in said substrate and fluidly connected to said descender, said nozzle having a fluid droplet outlet coplanar with an outer substrate surface; And
And two recirculation passages symmetrically disposed about and fluidly connected to each descender. The method of claim 17,
And said two recirculation passages are configured to allow fluid to flow from said descender to each of said two recirculation passages. The method of claim 17,
And the two recirculation passages are configured to allow fluid to flow from one of the two recirculation passages through the descender to the other of the two recirculation passages. The method of claim 17,
And the distance between the outer substrate surface and the closest surface of each recirculation passage is no more than approximately ten times the width of the outlet. The method of claim 20,
The outlet width is approximately 12.5 microns and the distance between the outer substrate surface and the closest surface of each recycle passage is less than approximately 60 microns. The method of claim 17,
And a flow rate (expressed in picolites per second) to the area of the outlet (expressed in square microns) passing through each recirculation passage is approximately 10 or greater. The method of claim 22,
Wherein the area of the outlet is approximately 156 square microns and the flow rate through each recirculation passage is approximately 1500 picoliters or more per second. The method of claim 17,
And the dimensions of said two recirculation passages are approximately equal to each other. A substrate on which a fluid pumping chamber is formed;
A descender formed in the substrate and fluidly connected to the fluid pumping chamber;
A nozzle formed in the substrate and fluidly connected to the descender;
An actuator in pressure communication with the fluid pumping chamber, the actuator capable of generating a firing pulse having a firing pulse frequency to eject fluid droplets from the nozzle; And
And a recirculation passage formed in said substrate and configured to have an impedance at a firing pulse frequency substantially higher than the impedance of said nozzle. The method of claim 25,
And the impedance of the recirculation passage at the firing pulse frequency is at least two times higher than the impedance of the nozzle. The method of claim 25,
And the impedance of the recirculation passage at the firing pulse frequency is at least 10 times higher than the impedance of the nozzle. The method of claim 25,
The impedance of the recirculation passage at the firing pulse frequency is high enough to prevent from the firing pulse energy loss from the firing pulse through the recirculation passage which significantly reduces the pressure applied to the fluid at the nozzle. Fluid droplet discharging device. The method of claim 25,
Wherein the firing pulse frequency has a firing pulse width and the length of the recirculation passage is substantially equal to the firing pulse width multiplied by the speed of sound in two separate fluids. The method of claim 25,
And the cross-sectional area of the recirculation passage is smaller than the cross-sectional area of the descender. 31. The method of claim 30,
And wherein the cross-sectional area of the recirculation passage is less than approximately 1/10 of the cross-sectional area of the descender. The method of claim 25,
A recirculation channel formed in said substrate and in fluid communication with said recirculation passage; And wherein the transition of the cross-sectional area between the recycle passage and the recycle channel comprises an acute angle. A substrate on which a fluid pumping chamber is formed;
An actuator in pressure communication with the fluid pumping chamber, the actuator capable of generating a firing pulse having a firing pulse width to eject the droplet from the nozzle;
A descender formed in the substrate and fluidly connected to the fluid pumping chamber;
A nozzle formed in the substrate and fluidly connected to the descender; And
And a recirculation passage formed in said substrate and fluidly connected to said descender, said recirculation passage having a length substantially equal to a firing pulse width multiplied by the speed of sound in two separate fluids. A substrate having a fluid inlet passage and a recirculation channel formed therein; And
And a plurality of flow path portions formed in the substrate, each comprising a fluid pumping chamber, a descender, and a recirculation passage, the plurality of passage portions fluidly connected in parallel between the fluid inlet passage and the recirculation channel. .

Images